Monitoring systems have been developed, the monitoring systems including a monitoring terminal that searches for an object set in advance by performing collation processing between an image of an object (for example, a person) included in a taken image obtained by imaging a predetermined position with an imaging unit and a registered image of the object set in advance.
Some of the monitoring systems extract a characteristic from the taken image obtained by imaging performed by the imaging unit, select a best shot image from the taken image based on an extraction result of the characteristic, and perform collation processing by using the best shot image. However, processing of extracting the characteristic is performed for all taken images, so that calculation cost of the monitoring terminal is increased. Some of the monitoring systems compose an image suitable for collation with the registered image by using all taken images obtained by imaging performed by the imaging unit, and performs collation processing using the composite image. However, due to the composition of the image, calculation cost of the monitoring terminal is increased.